Electric furnace for and process of heating substances uniformly and at a controllable temperature in an electric arc.



F. VONWILMOWSKY, DEGD.

E. J. PRINDLE, EXEGUTOR.

ELECTRIC FURNACE FOR AND PROCESS OF HEATING SUBSTANCES UNIFORMI-Y AND 4 AT A GONTROLLABLE TEMPERATURE IN AN ELECTRIC ARC.

APPLICATION FILED 0OT.28, 1896. 1,094,381 Patented Apr. 21, 191$ N mo W233 INVENTDR UNITED STATES PATENT OFFICE.

ERWIN IF. VON WILMOWSKY, OF BOSTON, MASSACHUSETTS; EDWIN J. PRIN'DLE, EXECU- TOR OF SAID VON WILlVIOWSKY, DECEASED, ASSIGNOR TO MRS. OLGA PIEPEB, OF

POTSDAM, GERMANY.

ELECTRICFURNACE FOR AND PROCESS OF HEATING SUBSTANCES UNIFORMLY AND AT A CONTROLLABLE TEMPERATURE IN AN ELECTRIC ARC.

Specification of Letters Patent.

Patented Apr. 21,1914.

Application filed October 28, 1896. Serial No. 610,286.

T 0 all whom it may concern Be it known that I, ERWlN F. voN VVIL- niowsnr, a citizen of the United States of America residing at the city of Boston, Commonwealth of Massachusetts, have invented certain new and useful improvements in electric furnaces for and process of heating substances uniformly and at a controllable temperature in an electric arc. and that the following is a description of the invention, which will enable those skilled in the art to which it appertains to make and use the same, reference being had to the different figures of the accompanying drawings, in which the same letters designate identical or analogous parts.

I have found that an arc-furnace in which the materials to be heated are brought directly into the arc and exposed to its influence, has the disadvantage that where the arc happens to pass, the substances which are to be heated will volatilize and forcibly be dispersed, causing considerable loss while the particles close by are heated insuiticiently, or too slowly, and,-although intense local heat is produced and much on orgy-is used,-but little useful effect is pro d need in the heating chamber.

it is the object of my invention to so con struct and proportion my apparatus that by suitable regulation a form of discharge may be maintained which will diffuse itself unifo-rmly between the electrodes, producing a temperature which is controllable andwhere desired-far lower than in electric furnaces known, and it is at the same time my aim to make the operation continuous.

My apparatus is constructed so that it gives generally a much reduced maximum temperature and a far increased temperature in most parts or the heating chamber. Hereby the useful effectof the expensive electrical energy is greatly increased.

The drawing illustrates a sectional elevation of a furnace and electrical connections adapted to carry out my invention.

The furnace, A, may be constructed with a cylindrical carbon lining, a, cemented to a carbon disk 0 to form a heatin chamber and one electrode. whilecentrally supported within this chamber is aimovable carbon-bar Z which is the other elect-rode. Carbon bush ings, (4 are cemetedto the heating chamber and contain carbon pencils (4 to conduct current to the chamber or draw an arc to start the furnace. with heat and electric insulating coverings 0.", and bound together with an iron sheathing a. A solenoid c is coiled around the covering a and insulated from the sheathing by an asbestos lining a. At the bottom of the heating chamber a discharge spout a7, is located. A chute, d, of insulating material supports and guides the movable carbon bar Z), and is provided with a sampling opening closed by a mica cover d. An inclined feeding tube 6, mounted in bearings and having means to rotate it, conducts the charge to the chute (Z, from the fixed hoper f.

The carbon bar 6, connects with one pole of the separately excited dynamo, g, the other pole being connected by switches, h, to portions of the chamber a, preferably to the carbon bushings of. The solenoid is connected in multiple to the furnace, with a suitable resistance, 2', (in series with the solenoid) with the dynamo g.

If the furnace is empty the bar, Z), may be lowered till it touches the disk 66, and lifted to draw an are. In a short time the chamber becomes filled with fine heated conducting matter, and current is now caused to traverse the solenoid. The are now moves around the bar and the bar is lifted gradually, so the arc moves outwardly warming more of the surrounding space and as long as enough current can pass the arc is sustained, but as increasing resistance is encountered it is finally disrupted. Said fine heated conducting matter consists of particles torn ofi or vaporized by the action of the electric current from the electrodes; said particles may be in solid or gaseous state and are highly conducting on account of their high temperature. These conditions will be clear when an ordinary arc lamp is examined either in operation or thereafter. On the inside of the globe and at the bottom some fine carbon dust will be noticed. As

soon as'the arc is disrupted, as mentioned before, the described method of starting is repeated until the bar is so high that the arc passes not any more to the bottom, but to the side of the chamber, becausethe distance is less. When the arcis extinguished from this The chamber is incased time it may be start-ed by the pencils a, without movin the bar 72, and while restarting the solenoid current is first weakened and then strengthened. The arc or arcs are permitted to revolve long enough to highly heat the furnace, and then the current is increased in the discharge path moderately and to some extent in the solenoid, thereby causing more rapid rotation of the arcs. This process is continued until a high temperature is attained when the increasing. current which is being forced through the arcs, as it is bounded above and below by portions of the electrodes at a lower temperature than the plane of motion of the arcs and hence of greater resistance, causes the arcs to spread in their plane of motion, mingling one with another and forming a uniform disk across the furnace. When this marked change in the discharge takes place, the rapid rotation ceases, the locally excessive temperature falls.

When nowas an experiment-the central carbon-bar is with its lower end brought in contact with the side of the furnace walls (making a short circuit) and quickly withdrawn to the previous central position, a peculiar phenomenon will be observed within the otherwise not afiected arc-disk which phenomenon consists in some slow-moving sharply-outlined, brightly-luminous matter (probably incandescent particles of the electrode material) passing from one electrode to the other in a spiral curve, proving absence of any quick rotating element at the level of the lower end of the carbon bar. The arc disk has a tendency to be at the said level in case the current supply is mainly from the top of the furnace (5.6. in case current connection to both electrodes is made mainly at the upper parts of the electrodes). The dependence herein referred to of the location of the electric discharge between I concentric cylindrical electrode surfaces upon the levels of energy-supply has-been more fully explained in an application Serial-Number 610285 filed Oct. 28 1896 simultaneously with the present case. The discharge current may now be varied and even decreased considerably without interrupting the peculiar form of discharge, and the solenoid current may now fall to an inconsiderable relative value, and in fact is only needed. to prevent abnormal but unavoidable conditions from wholly interrupting the discharge. Such conditions will arise from impurities in the electrode material and by the different volatility of the particles of the charge, in case the furnace is used for liquid or for solid charges. In this latter case the charge may be delivered through the rotating feeding tube 6, to the furnace, and suitable changes of the currents can be made, as may be de med necessary, from watching the operation through the mica,

03 The liquidor granular products of the reactions may be tapped oil by the spout, a", and the hot gases may pass off through the hopper, incidentally giving up their heat to "the fresh charge. When more heat is required, the discharge current is first increased and then if necessary the solenoid current when decreasing the heat the solenoid current'is first diminished and then the discharge current.

If a residue from a previous operation covers the disk, a then the furnace may be started by drawing arcs with thepencils, a energizing the solenoid and on extinction repeating the process till the arcs are maintained, and then following the above described process. When the heat is sufficient, the substances forming the residue are fused. and may readily be removed. With this furnace .the supply of energy can be given at anydesired level or levels. Which level answers best depends partly on the nature and on the distribution of the charge and on the speed of its motion, and is best determined empirically during the operation of the furnace by successively moving the several switches supplying energy to the outer electrode. l have found that theoperation can be influenced there by greatly and the Work when proceeding irregularly can frequently be made normal again by a change of the supply level or levels. This influence is seen even with gaseous charges 23. e. when the furnace is used to pass gases or vapors through to expose the same to the electrical energy. This influence is evidently based on the greater or less effect of the current-elements within the electrodes upon the d-ischarge'; but whatever may be its cause the influence itself is there and has been made use of herein. To demonstrate its existence the central carbonbar can serve: when the supply of energy came from the top level, said bar shows evidence that the arc-disk has emanated from the extreme end of the bar. And when the supply was given to the outer electrode at low levels, the appearance of the bar (0. g. the consumption of the surface-layer) and other evidence show that the arc-disk emanated uniformly from the lowest part of the carbon-bar for quite a distance i. c. that the disk had quite an appreciable thickness at the central electrode, which means that the temperature was far more uniform in the second case.

The above effect of the current within the electrodes'on the discharge combines sometimes with the effect which a quick up ard motion of hot gases or vapors has upon an electric arc and drivesthe'discharge-with disastrous results-upward on the central electrode in form of a flaming roaring rotating arc destroying the part of the furnace which holds the electrode. The fault 30 in such case has been that the energy was supplied at too low levels considering the speed of the gases. I have found a uniform and comparatively low temperature and its control not obtainable without a cylindrical reacting space or with an abundance of fresh. charge above the reacting space. The charge, therefore, should be added in a stream, not periodically in lots.

\Vith reference to the partly diagrammatical character of the drawings, it will be understood that the carbon-pencils a when in use for starting arcs, receive current from the carbon-bushings, in which they fit properly.

By the apparatus described herein I have discovered a new form of electric discharge which may simply be called a diffused discharge. It is markedly different from the known discharges which have generally well defined outlies. For establishing a diffused discharge it is essential to have a confined heating chamber. Y

I have discovered that in the apparatus described herein at comparatively low temperatures a diffused discharge can be maintained, though the same apparatus may be used for higher temperatures. then said diffused discharge has been well established, as described in the foregoing, a homogeneous luminous disk stretches itself across the tube forming the heating chamber, marking on the two electrodes rings or hands of entirely uniform and generally surprisingly moderate brightness, so far as the furnace is empty or so far as the character of the charge does not reduce the uniformity. No rotation whatever is visible in this form of discharge, and the electric energy appears to stream perfectly uniformly between said rings at any given moment, not preferring at any moment a special linear part. This disk, when only a few inches in diameter, is noiseless, except with alternating current, which besides requires, in order to form a disk, more amperes and more volts for the same apparatus. "Ji hen minimum energy (the way of doing it consists in forming a disk with. more energy first and then gradually reducing the en ergy-supply), and the tubular electrode as carbon the appearance of the discharge hardly is distinguished from the appearance immediately after the discharge has been suddenly stopped. The discharge looks as a very steady and not in the least differentiated pure blue Bunsen gasfiame of hardly unusual intensity. Evidently no solid mat ter is torn off from the electrode surfaces, as is the case in the known forms of are discharges.

VVhen the disk is once formed, any in crease in current will increase the luminosity and the temperature, which latter can be regulated with precision by regulating the. current-supply. When the electrode, 6, is moved even considerably out of its central position, the disk is not changed thereby in its appearance of uniform luminosity, and no motion in it is visible. N or is the disk affected by solid materials constituting the charge and falling through the same to the bottom of the furnace unless the energy-supply of the disk is too small for such work. The position of the disk is changed at will by lifting or lowering the central carbon electrode.

The temperature of the furnace when once started is changed or regulated by changing or regulating the supply of electrical energy, and it is remarkable that this supply can be varied within wide limits and the temperature at the same time without destroying the diffused character of the discharge. In consequence thereof the furnace described herein and operated so as outlined is useful for a far wider field of application than the electrical furnaces known. \Vhen the supply of energy is reduced too much the diffused character of the discl'iargc is changed into rotating arc discharge or the whole discharge is interrupted. "When the magnetism is sustained and the currentfor the disk reduced, the latter transforms at last quite suddenly into one or more quick rotating ares, emitting roaring noise even if the heating chamber consists of a carbon tube of less than two inches internal diameter. This quick transition from utter silence of a. discharge which is only moderately and perfectly uniformly luminous into one or more very bright rotating streamers of distinct outline is another striking feature proving the difference between diffused discharge and rotating arc.

The furnace is particularly fit to pass gases or vapors througl which are to be exposed to electrolytic and electrosynthet-ic forces or. to be heated to a certain tempera- "ture favorable to a desired reaction. such disk-discharge has been formed with as any local overheating is avoided in this furnace the yield of the el'ectro-chemical reaction or of the plain heat reaction for which the furnace is used is greatly in- Q creased. well as the central electrode consists of pure lVhile T have described an apparatus havmg circular electrodes it is not necessary i that such be used. it is only essential that the shape and location of the electrode should be suited to the work to be performed i and within the influence of the impressing electric and magnetic forces.

The apparatus may be operated either by dlrect or by alternating current. hen aljternating currents are used the current in :the solenoid and the furnace current must have the same period of alternation and the 'same phase. Both currents, therefore, are

taken from the same current generator and the regulating rheostats are practically free of self induction 2'. 6., it is avoided to use for regulation wire coils.

To distinguish my invention more clearly from certain ways in which a solenoid has been used heretofore, it may be added that to thermally isolate an electrical heating chamber is not a matter of economy only: lVhen radiation is permitted the local temperature is at first directly reduced and then the conductivity is reduced which depends upon the temperature. This means that between two points within the electric discharge space a smaller current passes and less energy is transformed and so the temperature indirectly reduced by the permitted radiation. Therefore, the uniformity of temperature in different parts of the reacting space can not be approximated when by the furnace-construction or its use (too much fresh charge) an essential degree of radiation is permitted.

In the operation of this furnace it is preferable the cylindrical character of the electrodes is essentially maintained. A. proper lifting of the carbon bar and handling of the switches supplying energy to the outer electrode is here required.

It has been stated in the above that there is an absence of any quick rotating element at the level of the lower end of the carbon bar. To avoid misapprehension, it must be noted that the main discharge is below said level if the current supply is mainly from above as explained in the above cited, simultaneously filed application. Besides, it may be considered as a fact that the molecules of the hot gas within the actual discharge space actually rotate around the central carbon-bar according to the principles of electric motors, though such rotation is visible only in the rotatin arc and not in the described diflused discharge. The essential difference is that the rotating arc has (radial) zones of excessive temperature alternating with such of comparatively far lower temperature. This feature also exists in certain apparatus used for ozonizing air wherein what issaid to be a diffusedndischarge is maintained, though actually a streaming or radiating of electric energy is noticeable (even with currents of very high frequency), which precludes the uniformity of temperature provided by the present invention. In all these matters the fundamental fact is that a, gas has a tendency to conduct electricity in streamers because particles of the gas heated by the electriccurrent arebetter electric conductors than the rest. Said tendency can be overcome by increasing the conductivity either by heat as in electric furnaces for graphitizing carbonrods or byvvacuum as in Geisler tubes. Now, the present invention gives a new means, of

practical value in many industries, for overcoming said tendency, which means may be said to consist substantially in devices for spreading an electric discharge in two directions vertical to each other and vertical to the current flow. The spreading in one of said two directions is done by the solenoid; the spreading in the other direction is done by suitably choosing the level oft-he current-supply. To give as an example some figures, a furnace intended for gases and for a small scale may have an inside diameter of one-and-one-half inch with a central carbon rod of one-half inch diameter, then a current of fifteen amperes at forty-five volts and a magnetic field of hundred-fifty ampere-turns will generally be sufiicient to give a homogeneous diffused disk-discharge if a low temperature is desired and continuous current used. The energy of an ordinary arc-lightof so-called thousand candlepower is spread herein so that it fills the space of about one-andone-half square-inches for a length of one-half inch or more dependent upon the gas-fiow, 'the quality of the electrode-material and above all upon the temperature existing at the time in the furnace.

Having thus described the nature of my invention what I claim is as follows:

1. In an electric arc furnace, thecombination of concentric cylindrical electrodes suitably spaced apart, the intermediate space forming the furnace chamber, of a solenoid whose magnetic axis coincides substantially with that of said electrodes, and a regulator in electrical circuit with said sole- I noid, substantially as described.

2. In an electric arc furnace, the combination of concentric cylindrical electrodes suitably spaced apart, the intermediate space forming the furnace chamber, of a solenoidwhose axis coincides substantially with that of said electrodes, independent regulators in electrical circuit with said electrodes and solenoid, respectively, and means 1 for supplying energy to the outer electrode 7 at different levels.

3. In an electric arc furnace, the combination of concentric cylindrical electrodes suitably spaced apart, the intermediate.

space forming the furnace chamber, of a solenoid whose magnetic axis coincides substantially with that of said electrodes, independent regulators in electrical circuit with said electrodes and solenoid, respectively,

substantially as described,-and means for establishing an arc between said electrodes.

4. In an electric arc furnace, the combination of concentric cylindrical electrodes suitably spaced apart, the intermediate space forming the furnace chamber, of a solenoid whosemagnetic axis coincides substantially with that of said electrodes," independent regulators in electrical circuit with said electrodes and solenoid, respectively, means for supplying energy to the outer electrode at different levels, said means consisting of carbon pencils movable through the outer electrode toward and from the inner electrode, and means for conveying current to any one of said pencils.

5. In an electric arc furnace, the combination of concentric cylindrical electrodes suitably spaced apart, the intermediate space forming the furnace chamber, means for closing the upper and lower ends of said intermediate space, and for permitting the continuous feed of material through said space, of a solenoid whosemagnetic axis coincides substantially with that of said electrodes, and independent regulators in electrical circuit with said electrodes and solenoid, respectively.

6. In an electric arc furnace, the combination of concentric cylindrical electrodes suitably spaced apart, the intermediate space forming the furnace chamber, means for adjusting said electrodes relative to each other in an axial direction, a solenoid whose -magnetic axis coincides substantially with that of said electrodes, and independent rogulators in electrical circuit with said electrodes and solenoid, respectively.

7. In an electric arc furnace, the combination of concentric cylindrical electrodes suitably spaced apart, the intermediate space forming the furnace chamber, the outer electrode being closed at one end, and the inner electrode being adjustable axially, of a solenoid whose magnetic axis coincides substantially with that of said electrodes, and independent regulators in electrical circuit with said electrodes and solenoid, respectively.

8. In an electric arc furnace, the combina tion of concentric cylindrical electrodes suitably spaced apart, the intermediate space forming the furnace chamber, of a solenoid whose magnetic axis coincides substantially with that of said electrodes, and independent regulators in electrical circuit with said electrodes and solenoid.

9. In a cylindrical electric arc-furnace groups of arc-starting devices located in different cross-sections of the furnace and provided with individual switches for the purpose of securing a uniform electrode-consumption and temperature, substantially as described.

10. In an electric furnace, the combination with an inclosed thermally insulated tubular heating chamber the walls of which constitute one of the electrodes, of a solenoid whose individual turns surround at least a portion of said heating chamber, and a second electrode extending within said chamber the space between said electrodes constituting the reaction space of the furnace, substantially asdescribed.

11. In an electric furnace, the combination with a heating chamber the inner walls of which constitute one of the electrodes, of a solenoid surrounding said heating cham her, a second electrode extending within said chamber, and a plurality of movable extensions of said wall electrode projecting into said chamber and accessible from the outside thereof, substantially as described.

12. In an electric furnace, the combination with a heating chamber constituting the reacting space for the charge, and suitable electrodes having their, \vorking surfaces within said heating chamber, of means for producing between said electrodes a diffused electric discharge, substantially as described.

13. In an electric furnace, the combination with a confined highly heated chamber within which is comprised the reacting space for the charge, and suitable electrodes hav ing their working surfaces within said heating chamber, of means for producing between said electrodes a diffused electric dis charge in at least a lower portion of said chamber.

14. In an electric furnace, the combination with a heating chamber constituting the reacting space for the charge, and suitable electrodes having their working surfaces within said heating chamber, of means including a solenoid,within which said heating chamber is located, for producing between said electrodes a diffused electric dischar e at a comparatively low working temperature.

15. The process of electric furnace working which comprises forming in a heating chamber a diff used electric heating discharge, and passing through said discharge the substance to be acted upon, substantially as de scribed.

16. The process of electric furnace working which comprises forming an electric are or arcs, compelling such are or arcs to lose distinct identity and coalesce in a diffuseddischarge, and then passing through said discharge the substance to be acted upon, substantially as described.

1?. The process of electric furnace working which consists in forming an electric are between opposed electrodes, and subjecting such arcs to suitable electric influences, compelling such arcs to lose distinct identity and coalesce in a diffused discharge, then passing through said discharge the substance to be heated, substantially as described.

18. The process of electric furnace worlc ing which consists in forming an electric are or arcs between opposed electrodes, one of which electrodes inclosing the other, and subjecting such arcs to suitable electric influences, causing such arcs to lose distinct identity and coalesce in a diffused discharge, and passing through said discharge the substance to be. heated, substantially as deing which consists .in forming an electric are or arcs between electrodes, one of which electrodes has a substantially cylindrical inner surface and incloses the other electrode, subjecting such are or arcs to suitable electro-magnetic influences and thereby causing such are or arcs to lose distinct identity and. coalesce in'a diffused disk-like discharge, and passing through said discharge the substance to be heated, substantially as described.

20. In an electric furnace, the combination of a heating chamber, a solenoid, the heating chamber being in the plane of and inclosed by individual coils of the solenoid.

21. In an electric furnace, the combination of a heating chamber, means for producing an arc in said chamber, and a solenoid, the heating chamber being in the plane of and inclosed by individual coils of said solenoid. 7

22. In an electric furnace, the combination of a heating chamber, means for producing an arc in said chamber, and means for diffusing said are.

28. In an electric furnace, the combination of a heating chamber, means for producing an arc in said chamber, and a solenoid surrounding said chamber, said solenoid having sufficient capacity to diffuse the arc.

24:. In an electric furnace, the combination of-a heating chamber, means for producing an arc in said chamber, and magnetic means for difi'using said arc.

25. In an electric furnace, the combination of a heating chamber and a solenoid, the heating chamber being inclosed within individual coils of the solenoid, and the solenoid being embedded within the walls of the heating chamber.

26. In an electric furnace, the combination of a heating chamber, means for substantially fillin the cross-section of said chamber-with an electric discharge, and

'-means for passing material through said cross-sectlon.

27. In an electric furnace, the combination of a heating chamber, means for substantially filling the cross-section of said chamber with a sheet of electricity, and

means for passing material through said and assume of alternating current connected with said solenoid.

30.'In an electric furnace, the combination of a heating chamber, a solenoid, a portion of said heating chamber beinginclosed within and in the plane of an individual coil of said solenoid, and a source of alternating current connected with said solenoid.

31. In an electric furnace, the combination of a heating chamber having two electrodes, means for making a short circuit between said electrodes, and means for diffusing the arc thus formed.

32- In an electric furnace, the combination of a hollow electrode forming a heating chamber; a second electrode, means for forming. a short circuit between said electrodes, and means for diffusing the arc thus formed.

33. In an electric furnace, the combination of a hollow electrode and a second electrode, a pencil for forming a short circuit between said electrodes, and means for dif fusing the are thus formed.

34:. In an electric furnace, the combination of a heating chamber, a solenoid having individual coils surrounding said heating chamber, said heating chamber being in the plane of said coils, and means for forming an arc in said heating chamber, said solenoid being of such capacity as to form a magnetic field strong enough to diffuse said arc.

35. The method of producing a diffused electric discharge, consisting in causing an arc to flow between electrodes, causing such are to move by magnetism, and then increasin the current until a diffused discharge talies place.

36. The method of producing a diffused electric discharge, consisting in causing an arc to flow between electrodes, causing such are to move by magnetism, then increasing the current until a diffused discharge takes place, and then decreasing the current.

37. The method of producing a difiu'sed electric discharge, consisting in causing an arc to flow between c1rcular-electrodes,causmg such arc to rotate by passing llnes of magnetic force parallel to the axis of such electrodes, and then increasing the current until a diffused discharge takes place.

38. The method of producing a diffused.

electric discharge, consisting in causing an arc to flow between cylindrical electrodes, causing such are to rotate by passing lines of magnetic force parallel to the axis of such electrodes, and then increasing the current untiladiffused discharge takes place.

39. The method of producing a diffused electric discharge, consisting in causing an arcvto flow between circular electrodes, caus ing such are to rotate by assin magnetic force parallel to t e axis of suchlines of electrodes, then increasing the current until a difiused discharge takes place, and then decreasing the current.

\ 4:0. The method of producing a diifused electric discharge, consisting in causing an arc to flow between circular electrodes, causing vsuch arc to rotate by passing lines of magnetic force parallel to the axis of such electrodes, and then increasing both the magnetism and the current until the diffused discharge takes place.

I 41. The, method of producing a diffused electric discharge, consisting in causing an arc to flow between cylindrical electrodes, causing such are to rotate by passing lines of magnetic force arallel to the axis of such electrodes, and t en increasin both the magnetism and the currentunti a diffused dischar e takes place.

42. T e method of producing a diffused electric discharge consisting in causing an arc to flow between circular electrodes, causing such are to rotate by passing lines of magnetic force parallel to the axis of such electrodes, then increasing the current and afterward the magnetism.

43. The method of producing a diifused electric discharge consisting in causing an arc to flow between circular electrodes, causing such are to rotate by passing lines of magnetic force parallel to the axis of such electrodes, then increasing the current and afterward'the magnetism, and then decreasing the magnetism and afterward the cur rent.

44. The process of electric furnace working which comprises forming in a heating chamber a diffused electric discharge.

&5. The process of electric furnace working which comprises forming in a heating chamber an electric arc, and increasing the volume of said are beyond its normal volume in still air.

46. The process of electric furnace Working which comprises forming in a heating chamber a difiused electric discharge, and passing gases through said discharge.

In testimony whereof, I have signed my name in presence of two witnesses, this twenty-seventh day of October, 1896. v

ERWIN F. VON WILMOWSKY. Witnesses:

Orro E. Siemens, ARTHUR SMITH. 

